Nonreciprocal gyromagnetic waveguide device with heat transfer means forming a unitary structure



Oct. 29, 1968 G. L. HEITER 3,408,597

NONRECIPROCAL GYROMAGNETIC WAVEGUIDE DEVICE WITH HEAT TRANSFER MEANS FORMING A UNITARY STRUCTURE Filed May 11, 1966 w R US m EE DH FIG. .3

FIG. 4

A TTOP/VE V Patented Oct. 29, 1968 States Patent Ofiice II I II II member is less than permanent in that its location is sub- NONRECIPROCAL GYROMAGNETIC WAVEGUIDE ect to variations that may occur during the mechanical I DIEVIIICE WITH H TRANSFER EA S ORM. assembly or during the operation of the device, or both. G A UNITARY STRUCTURE George L. Heiter, Whippaiiy, N. assignor to Bell 5 vide an efficient heat transfer path from an element with- Tel'phoueLaboratories; ncorporated, New York, i a Wave I I I I guide to the exterior thereof. I II n-y-r i g ggg l {ggfggfg 549 325 It is another object of this invention to provide a simple I 4 CIaimSI 333 z4I1) method of constructing a waveguide device with a heat sink "to provide an' effective means for removing heat f q g f a l element I I the waveguide walls to a heat sink. The waveguide device I I I I I I I I I is constructed by bonding a pair of dielectric heat transfer This invention relates to electromagnetic energy trans- HIHSSIOII devices and more particularly to waveguide dean attachment to a heat sink.

. l The present invention will be better understood upon Waveguide devices frequently have internally disposed elements suchgas Icors which interact with the electro consideration of the following detailed description when t taken in conjunction with the accompanying drawing in magnetic energy-propagating within. These elements are which,

often composed of gyromagnetic materials to provide nonreciprocal operation These nonreciprocal waveguide i f gg g zgz g iggi z 3 55 1 2: gig: devices employing gyromagnetic materials are frequently p v described; and

lim ted n their power handling capabilities because the FIGSI 2 through 5 illustrate a method of practicing the invention.

5 The invention is illustratively set forth in the context of a latching type digital ferrite phase shifter shown in tobe altered in' an undesirable fashion. -Vario'us attempts have-been made to overcome this 40 so that an incremental phase shift of can be introduced to electromagnetic energy propagated within the guide by the judicious application of current pulses to coils individually Wound through the apertures of each core. Illustratively, core 2 may be composed of some gyromagnetic material such as ferrite or garnet and coil 5 may be Wound through the aperture of core 2 to produce a remanent field within the core in response to current pulses. This remanent magnetic field interacts with the circularly polarized components of the electromagnetic waves to introduce a phase shift having a magnitude dependent upon the direction of remanent field within the core. Each of the other cores may also have a winding which, when pulsed, controls the phase shift introduced by the device.

The temperature within each of the cores increases by virtue of the absorption of energy as the propagating electromagnetic energy level increases. Since the thermal contact each of the cores makes with the top and bottom faces of the waveguide and the thermal conductivity of the core material are insufi'icient to provide for the removal 'of the heat generated when the device is operated at hightend lIO'l'UPtlllC the bond anddestroy the effectiveness of with the outer conductor and the ferrite elements within Power levels, the present inven ion provides additional 'i' composed of a metallic material having springqike heat removal paths in the form of dielectric heat shunts properties which are utilized in positioning the member 8 and 9 Placed on either Side of the core- Each of these 'Within the waveguide. However, the metallic composiheat shunts extend longitudinally within the waveguide on tion of the heat transfer member results in some uneither side of the longitudinal array of cores so that one wanted radio frequency magnetic field distortions. Furwal-l makes thermal contact with a wall of the core array.

thermore, this method of positioning the heat transfer The remaining three walls of each of these dielectric heat shunts are respectively in thermal contact with a side wall and the upper and lower walls of the waveguide to provide an efiicient heat transfer path between the core and the waveguide. Heat sinks such as plates 10 and 11 can be fastened to the waveguide surfaces to provide for the removal of the heat transferred to the waveguide from the core. The particular heat sink employed can be selected to comply with the needs of the specific device and accordingly, for example, plates 10 and 11 may be provided with circulating coolants.

The method by which the illustrative device is produced is shown in FIGS. 2 through 5. One longitudinal wall of each of the dielectric heat shunts 8 and 9 is bonded to one wall of the longitudinal array of cores 2, 3 and 4 (as shown in FIG. 2) to form a mandrel (as shown in FIG. 3) over which the waveguide is electroplated. The core array of FIG. 2 is obtained by stacking cores 2, 3 and 4 end to end with separators in the form of dielectric slabs 12 and 13 bonded between the ends of abutting cores. The cross-sectional dimension of these dielectric slabs are selected to conform with those common to each core. As illustrated in FIG. 3, the dielectric heat shunt forms 8 and 9 are then bonded respectively to either side of this longitudinally stacked array. The cross-sectional dimensions of the core and the dielectric forms bonded on either side thereof are selected to form a mandrel having the overall internal cross-sectional dimension (within a permitted tolerance) of the waveguide that is desired. It is to be emphasized that though a mandrel having a rectangular cross section is shown, any desired cross section may be obtained by using suitable shaped dielectric forms.

The bonding material should be selected to provide the adhesive properties required with a minimum thickness between the bonded surface. Furthermore, the bonding material must be thermally conductive and not be such as to introduce excessive loss to the propagating microwave energy. In order to prevent the destruction of mechanical properties of the ferrite core when the material is heated, it is desirable that the bonding material also have the ability to cure at room temperature. It is also desirable for the bonding material to have a degree of pliability after curing in order to absorb the operational stresses created by temperature variation.

A bonding material that has been found to satisfy these requirements is an epoxy mixture containing 100 parts by weight of a base resin such as Epon 828 made by the Shell Chemical Corporation, 40 parts by weight of polysulphoride rubber such as LP made by the Thiokol Chemical Corporation, and 20 parts by weight curing agent such as T1 hardener made by the Shell Chemical Corporation.

The dielectric forms 8 and 9 should be constructed from a material having sufficiently good thermal conductivity to be able to conduct away all the heat that reaches to the core surface. It must also have good microwave properties in that it should introduce little loss to propagating microwave energy and have a compatible dielectric constant. Additionally, the dielectric material used for the forms must have good mechanical properties in order to withstand the pressures created during the plating process and the pressures existing during the normal operation of the assembled device. Dielectric materials which satisfy these requirements include alumina, forsterite, berrylia and magnesium titanates.

The dielectric forms 8 and 9 are constructed with a longitudinally extending cavity in order to minimize the loss and dielectric loading otherwise introduced to propagating microwave energy. Also, the a erture of each of the cores may be filled with a dielectric material chosen for maximum differential phase shift per unit length of material and for minimum sensitivity to manufacturing dimensional tolerances in accordance with techniques understood by those versed in the art. Additionally, the dimensions of the core apertures are selected to obtain maximum differential phase shifts per unit length of core material in accordance witn considerations farni those versed in the art. The thickness of the walls of dielectric forms 8 and 9 is determined with knowledge of the fact that as the thickness increases the differential phase shift decreases while the efficiency ofheat transfer increases. 1 ff-' After the core-heat'shunt, man v manner described, holes parallel ,to,the broad",wall ,the waveguide are drilled through dielectfic forrnjfi"and through each of th dielectric sQParatOrsJZ and li -along a path abutting the ferriteLcOre Ascan. b'e Zseen from FIG. 3, a conductor (e.g., conductorfi) is then inserted through the drilled holes and aperturepf each core. Vinyl insulation is then placed oyetj the conductor where it emerges from the mandrel. One end-of the insulation is bonded and sealed at themandrel exterior .wallandgthe other end is extended beyond the conductoranghheat sealed. If a dielectric separator isinotplaced atthe exposed ends of cores 2 and 4 the insulation is retained withinthe core aperture for removal after the electroplating, .is completed. .1

The next step in the method for producing the device comprises sealing off all exp sed mandrel surfaces over which deposition of waveguide material is unwanted. One technique includes selecting a'pai'r of'brass plates 20 and 21 with dimensions at least, as large as the cross-sectional dimensions of the mandrel. ,One brass plateis then placed on each end of the mandrehwith arubber gasket (e.g.; elements 22 and 23) separation and this entireifissernbly is securely fastened by a C-clamp; With all of ther openings in the mandrel thus hermetically sealed, an electroless deposition of a metal such as copper or nickel is plated over the mandrel surface (as shown in FIG. 4) to -approxi. mately a tenth of a mil thickness. This, dep0sition provides a conducting interface between the insulating mandrel materials and the. additional thickness ,of metal-which is then electroplated (as shown in FIG. 5) over the electroless deposition, to formthe waveguide. The total thick ness of the waveguide can be on the order of 10m 50 mils;

After the waveguide is plated over the mandrel, the ,C-, clamp, brass plates and rubber gasketsare removed. The copper conductors running through each core are extended and the assembly can be clamped to a,s uitable heat sink. As shown in FIG. 1, a unitary structure with each element securely and permanently positioned isthusformed. In particular, dielectric forms 8 a nd 9 make permanent and excellent thermal contact with both the cores: andthe waveguide surface to efficiently transfer heat generated in the core to the waveguide walls and heatsinksa Addi-. tionally, because of the unitary nature of the device, 1116: chanical stresses created by -,virtue of temperatureQ-grm dients can comfortably be withstood by thestructure,with-, out any rupture of bonds existing amongst the elements;

While the invention is illustrativelyset forthinthe, form of a latching type digital ferrite phase shifterien closed within a rectangular waveguide, otherccrossesection geometries for this type device and, indeed, other devices such as isolatorsand circulators may. be: con-1 structed according to the teachings of'the invention set forth herein. For each device a mandrel which includes an internally disposed gyromagnetic' element. is'- constructed to conform' to the waveguide cross-sectional shape desired. A deposition of waveguide metal over the mandrel completes the assembly of'the device desired, It is to be noted that 'the'device illustrated na acon; structed by a process other than that described 'su ch 'as for example, forcing or sliding the heat shunt-core subassembly into a preformed waveguide. f

It is therefore to be understood "that the'abbW-d scribed arrangements are illustrative of ,the applications: of theprinciples of this invention Numerous other ar; rangements may be devised by.those skilledin the art without departing from the spirit andscope of the in-, vention. I

6 What is claimed is: positioned element, said coil having end terminals exterior 1. A waveguide device comprising: an internally posito said device. tioned element composed of 'gyromagnetic material and 3. A waveguide device in accordance with claim 2 positioned to produce non-reciprocal type operation in wherein the electroplated mandrel is clamped to a heat said waveguide; means for providinga heat transfer path 5 sink. from said element, said means including a mandrel hav- 4. A waveguide device in accordance with claim 3 ing' a pair of thermally conductive dielectric forms conwherein each of said dielectric forms includes an internal tiguously disposed with and: bonded to said element to cavity to prevent dielectric loading of said device. produce a geometrical configuration identical to said Waveguides internal cross-sectional dimensions; and a w Referen? cued layer of electrically conductive material disposed about UNITED STATES P T N said mandrel to form a unitary structure, said layer deposited about said mandrel including an electroless dep- X2: a z 333* X osition contiguous to said mandrel and an electroplated 3246262 4/1966 Wicgert 333 241 X layer plated over said electrolessly deposited layer. 15

2. A waveguide device in accordance with claim 1 AN KARL SAALBACH, Primary Examiner.

PAUL L. GENSLER, Assistant Examiner. 

